1. Field of the Invention
This invention relates to a compact or small scale switch which opens the connection of a circuit so as to protect it when an overcurrent flows therethrough and to a method of manufacturing the same.
The invention also relates to a method of mounting a bimetallic plate in this type of compact switch.
The invention further relates to a method of mounting a movable spring member for use in this type of compact switch.
2. Related Art
A type of conventional compact switch is known such as the one disclosed in U.S. Pat. No. 4,510,479 in which a bimetallic plate interposed in an electrical connection line is bent by the heat generated when an overcurrent flows through the bimetallic plate so that a movable contact is brought into contact with, or moved from, a fixed contact by a snap action of a movable contact element supporting the movable contact. This type of compact switch is assembled in such a manner that necessary precision parts, including terminal members which constitute the body of a switch unit, a bimetallic plate, a movable contact element, and a fixed contact element, are respectively incorporated directly in a housing by manual operation. That is, in the process of assembling this type of compact switch, the bimetallic plate is angled so as to be set to a predetermined position after it has been fixed to a terminal member which is one of the constituents of the switch unit body, and the terminal member to which the bimetallic plate has been fixed and other necessary precision parts are thereafter incorporated into the housing directly and separately from each other by manual operation.
Also, in this type of conventional compact switch, the mechanism of the movable contact element that effects a snap action is constructed by using a movable spring member, and this movable spring member is independently and directly incorporated in the housing by manual operation.
However, in manual assembly, much time and labor and a great deal of concentration are required. This means that assembly process is complicated by having many steps of precision production, and the possibility of human errors and the total manufacturing cost are therefore increased.
Also, there is a possibility of changes occurring in the bending characteristics of the bimetallic plate when the plate per se is angled.